DE4038331C1 - Compatible TV transmission system - forms groups from sequential lines of 16.9 side ratio image signals and separates out 3 lines from each gp. for spatial compression - Google Patents

Abstract

A compatible TV signal transmission system allows pictures with a 16:9 format to be transmitted in compressed form (20) with a 4:3 ratio. The difference in information between the two formats is respresented by information in lines along the top and bottom edges of the picture. At the receiver side the signals are reconstituted as a full 16:9 format signal that can be displayed on a suitable receiver (70). Alternatively, the 4:3 format version is used with a compatible receiver (80). ADVANTAGE - Creates compression algorithm whose low pass filter effect permits a high grade filter without having to use more than a quarter of the original number of lines for the transmission of additional information.

Description

The invention relates to a compatible transmission system according to the preamble of claim 1. A Such a transmission system is from DE-PS 38 40 054 known.

It turns out for improved television transmission systems for reasons of public acceptance than required, the aspect ratio of the television receiver from previously 4: 3 to 16: 9 (= aspect ratio of the HDTV standard and required aspect ratio of the new PALplus standard) without increasing compatibility to lose to existing television standards (PAL, NTSC, SECAM).

For this purpose it is proposed in DE-PS 38 40 054 on the transmitter side First separate every fourth line of the image signal and compress the remaining lines spatially or in correct spatial position to interpolate so that the Image height reduced to 3/4. In the released spatial Rooms are separated at the top and bottom of the picture fourth lines added directly or in a scrambled form. From the received decoded picture signal that original image signal with the aspect ratio of 16: 9 reconstructed by the fact that the upper and lower  Lines added to the picture edge after successful decoding decompressed in the correct spatial order into the remaining spatial Lines are inserted. The algorithm for Compression is designed so that in the 16: 9 receiver from the spatially compressed image signal and from the lines that am the top and bottom of the picture were added to the original Image signal can be completely reconstructed can. When playing the received signal on a conventional 4: 3 TV receivers are the ones at the top and Coded lines or line information added to the lower edge of the picture invisible when the receiver is correctly matched.

Through the algorithm to compress and expand the Image signal becomes the original image signal of a vertical Low pass filtering subjected to the resolution reduced in the vertical direction. In the procedure in Ratio 3: 4, the image signal is so strongly vertically low-pass filtered, that for the comparatively received image signal an unacceptable impairment of the vertical resolution, d. H. a vertical loss of sharpness, is achieved. This is due to the number limitation of the lines in the group formation, during the spatial Compression. There each group consists of four successive ones Lines. These four lines become one line derived as additional information. Furthermore, the four Lines according to DE-PS 38 40 054, d. H. interpolated on three lines. These three lines are as visible picture content transfer. This interpolation creates the vertical one Low pass filtering. This filtering is through group formation limited to filter grade 5.  

In order to achieve low-pass filtering, the image content of the compatible image is only slightly imperceptibly vertical it is necessary to use interpolation algorithms that one enable a higher degree of filtering than known algorithms.

The object of the invention is now a compression algorithm to create its low-pass filter effect a higher degree filter allows without more than 1/4 the original number of lines for the transmission of additional information must be used.

This object is achieved by the characterizing Features of claim 1 solved.

The invention is based on the consideration that if one only allows separate grouping, filtering with A higher degree can only be achieved if you are per group transmits more than just one line of additional information. This is not possible because the transmission channel is only over has limited capacity. To work around this problem sees the invention in the spatial compression of the image content an overlapping group formation.

The invention is based on an embodiment with With the help of drawings explained. It shows

Fig. 1 is a block diagram of the transmitter-side arrangement in an embodiment of the television transmission system according to the invention;

Fig. 2 is a block diagram of the receiver side arrangement in the television transmission system of Fig. 1, and

Fig. 3 is a block diagram of a compression means in the television transmission system of FIG. 1.

In the block diagram on the transmitter side according to FIG. 1, 10 denotes an image source which scans with a raster corresponding to an enlarged aspect ratio of 16: 9. In the illustrated example, the image signals generated by the image source 10 correspond to a conventional standard, with the exception of the changed aspect ratio at the receiver 70 . According to the PAL standard, each television picture comprises 575 active picture lines.

The output signal of the image source 10 is fed to an image signal processing stage 20 , which generates a spatial compression of the image in a ratio of 3: 4 from each group of n successive lines of the image signal. The 575 active lines of the image source 10 are thus compressed to 431 lines. The generated 431 compressed lines are again in the correct spatial position in the center of the image, as is shown with the aid of the compatible receiver 80 with an aspect ratio of 4: 3. Every fourth line is separated from the image signal generated in the image source 10 and transmitted to the 431 compressed lines as an invisible additional signal in the released spatial spaces at the upper and lower edge of the image. The exact way of sorting will be discussed later. A line folder 30 takes over the sorting of the lines to be transmitted, so that the visible 431 lines come to lie in the correct spatial position. The 575 active picture lines rearranged in this way are fed to a picture modulator 50 after a PAL or better after an I-PAL-M coding in the coder 40 and are transmitted via a transmitting antenna 60 . In the coder 40 , no color support is added to the lines of the spatial spaces at the top and bottom of the image, that is to say the additional information, so that they cannot interfere with the compatible receiver 80 .

The receiving side of FIG. 2 is divided into two areas. On the one hand, there is the compatible reception of the improved television transmission system on a conventional television receiver 140 with an aspect ratio of 4: 3, and on the other hand the reception of the improved television system on a wide-screen receiver 260 with an aspect ratio of 16: 9.

In the compatible reception of the television signal on a conventional receiver, the modulated image signal is received by the antenna 110 and is then demodulated in the image demodulator 120 to an image signal which, after passing through a standard PAL decoder 130, is applied to a receiver 140 with an aspect ratio of 4: 3 can be represented. The spatially compressed image signal of the image source 10 from FIG. 1 comes to lie on the picture tube of the compatible receiver 140 in the center of the picture. At the top and bottom of the image, a black stripe will be visible, which invisibly contains the additional information in the form of the luminance information of the separated lines of the image source 10 .

When the image signal is received on a wide-screen receiver 260 , the modulated image signal passes via antenna 200 to image demodulator 210 and then to a PAL or I-PAL-M decoder 220 . After decoding has taken place, the image signal is written into an image memory 230 . The image memory 230 keeps the image information of an image available until the line reordering in a stage 240 and the regeneration of the original lines in a subsequent stage 250 have been completed. The stage 240 transfers to stage 250, on the one hand, the additional information which is located in the edge lines at the top and bottom of the screen, and the image lines which are in the center of the image of the transmitted image signal. The regeneration of the original lines in stage 250 is described in more detail below. The decompressed image signal will be seen on the widescreen receiver 260 with an aspect ratio of 16: 9 without deterioration to the image source signal 10 .

The algorithm for the spatial compression of the image source signal 10 looks as follows. Groups are formed from all lines of the additional signal from n successive lines. In the exemplary embodiment under consideration, n = 6 is used. The lines of the image source signal 10 are successively labeled A, B, C, etc.

When the groups are formed, groups of n lines are formed from the successive lines of the image source signal 10 . The groups overlap each other in n-4 lines. In example Table 1 the first group from rows A, B, C, D, E and F. The second group is formed from rows E, F, G, H, I and J. The following groups are formed accordingly. The 1st group and the 2nd group overlap in lines E and F. Depending on the size of n, the groups overlap more or less.

Lines are separated from each group for additional information be transmitted. From the n lines of the first Group the first n-4 lines are separated and as additional information transmitted in the visible image area. Of each Group, including the first, becomes the last line transmitted as additional information at the top or bottom of the image. In the example in Table 1, those selected as additional information are Lines marked with an *. Be from the 1st group transfer lines A and B in the visible image. The Line F of the 1st group is in the spatial space at the top, or transferred lower edge of the image. From each additional group the last line as additional information at the top or transferred lower edge of the image. In the second group this is row J.

Three lines are separated from each group. These three Lines are interpolated from n-2 successive lines. The second separated line is spatially shifted to the first. The third separated line is to lines one and two spatially shifted. The shift is with the coefficients for interpolation so that the three separated Lines in the compressed image are spatially correct come to lie. In the following an example for n = 6.

Example of line interpolation on the send side for the 16: 9 format and for group formation with n = 6:  

Table 1

The calculation rule for the spatially compressed Lines reads:

X = a₁A + b₁B + d₁C + d₁D
Y = a₂B + b₂C + c₂D + d₂E
Z = a₃C + b₃D + c₃E + d₃F

x = a₁F + b₁G + c₁H + d₁I
y = a₂G + b₂H + c₂I + d₂J
z = a₃H + b₃I + c₃J + d₃K

Fig. 3 shows the block diagram of the spatial compression. The image signal on the input side is delayed or buffered several times by one line via line memory 300 . The matching first pixels of each line are weighted with the coefficients a₁ to d₃ and the results are added via summers 310 to the compressed lines X, Y and Z.

The compatible 4: 3 television receiver only evaluates the 431 interpolated lines and the first two additional lines for the 16: 9 format. In the improved widescreen receiver all 575 active lines will match the following Table 2 reconstructed.

Examples of line reconstruction in the 16: 9 widescreen receiver

Table 2

The original image lines of the image source signal 10 can be reconstructed from the received, spatially compressed lines and the received additional information. For this purpose, the received picture lines are linked with the received additional information as follows.

In the example for n = 6, the lines from the first group X, Y, Z received as spatially compressed picture lines. From the received lines are the additional information that from the picture (first group) as well as from the top and lower edge of the picture, after weighting with appropriate Coefficients, from the received image lines X, Y and Z subtracted.

X ′ = X - a₁A - b₁B
Y ′ = Y - a₂B
Z ′ = Z - d₃F

The intermediate results then obtained X ', Y' and Z ' used as follows to replace the original image lines α, to get β and τ again:

The following groups are treated accordingly. Only there for the additional lines that are in the first group from which image information was obtained, lines used in the calculation of the previous group have already been determined. Again, the overlap How the algorithm works clearly.

Claims (3)

1. TV transmission system compatible with conventional television standards, in which

• a) an image source is scanned on the transmission side with a raster corresponding to an enlarged aspect ratio of 16: 9, the lines of the 16: 9 image signal are reduced by spatial compression to an aspect ratio of 4: 3 while maintaining the essential image information, which reduced, spatially compressed image signal is transmitted as visible information, the difference signal from the 16: 9 image signal and the spatially compressed image signal is transmitted as additional information in the line area of the upper and lower edge of the image, and
• b) the original 16: 9 image signal is reconstructed and reproduced on the receiving side in a 16: 9 television receiver from the spatially compressed image signal and the additional information, while in a conventional 4: 3 television receiver the spatially compressed image signal in the central screen area with upper and lower margin is reproduced,

characterized by the following additional features:

• c) Groups of n successive lines are formed from all successive lines of the 16: 9 image signal, adjacent groups overlapping in n-4 lines and n being an integer greater than four;
• d) 3 lines are separated from each group, spatially compressed and interpolated in the correct spatial position;
• e) the first n-4 lines are separated from the first group and transmitted as further additional information in the visible image area;
• f) in the remaining visible area, the interpolated 3 lines are transmitted from each group;
• g) the last line of each group is transmitted as additional information and
• h) the 4: 3 and the 16: 9 television receiver additionally evaluate the additional information which is transmitted in the visible image area for the image reproduction.

2. TV transmission system according to claim 1, characterized characterized in that n = 6 is chosen.